CN100463180C

CN100463180C - Ferroelectric film, ferroelectric memory, and piezoelectric element

Info

Publication number: CN100463180C
Application number: CNB2005100025230A
Authority: CN
Inventors: 木岛健; 宫泽弘; 滨田泰彰
Original assignee: Seiko Epson Corp
Current assignee: Crystal Leap LLC
Priority date: 2004-01-20
Filing date: 2005-01-20
Publication date: 2009-02-18
Anticipated expiration: 2025-01-20
Also published as: TWI267188B; US20050167712A1; JP2005209722A; EP1557481A3; KR100598747B1; JP4171908B2; EP1557481A2; TW200531261A; KR20050076654A; CN1645617A

Abstract

The present invention provides ferroelectric films with which highly reliable ferroelectric devices can be obtained. A ferroelectric film comprised of a perovskite structure ferroelectric shown by ABO3, including at least one type of Si2+, Ge2+ and Sn2+ as an A site doping ion, and at least Nb5+ as a B site doping ion.

Description

Ferroelectric film, ferroelectric memory and piezoelectric element

Technical field

The present invention relates to a kind of ferroelectric film.In addition, the invention still further relates to a kind of ferroelectric memory and piezoelectric element that comprises ferroelectric film.

Background technology

Known conduct ABO ₃The perovskite structure ferroelectric of expression has Pb (Zr, Ti) O ₃(PZT).

So far the PZT based material that uses in ferroelectric memory (FeRAM) generally uses the material of the compositing range of B position in the Mixed Zone of cube crystalline substance of Zr/Ti=52/48～40/60, rhombohedral crystal.Because reliability is high and low-cost viewpoint, FeRAM so far mainly adopts above-mentioned composition.

But in this zone, the round and square property of so-called P-E magnetic hysteresis shape is insufficient.Magnetic hysteresis shape circle is explanation, and in polarization reversal, the reversal voltage during each polarization composition counter-rotating exists from low to high with having nothing in common with each other.This is because polaxis is different in cube crystalline substance of PZT and rhombohedral crystal, is (001) in cube crystalline substance, is (111) in rhombohedral crystal.That is, magnetic hysteresis shape circle is explanation, if apply current potential arbitrarily, reverses gradually from the polarization composition in the low-voltage counter-rotating, and data may be eliminated.That is to say just have the weak one side of data retention characteristics originally.What the FeRAM that uses adopted so far is to allow 3～5V of 3 times of the reactance voltage (Vc) of magnetic hysteresis displacement to a certain degree to drive.

In addition, the batch process of FeRAM, the MPB from PZT formed (the phase boundary coexisting phase of cube domain and rhombus domain) originally, its high reliability is an evidence rule of thumb, and is original, should have the PZT of the compositing range of high reliability, owing to other reason, destroy reliability.Therefore, in order to improve the square property of P-E magnetic hysteresis shape, all polarize composition preferably at identical voltage by the while polarization reversal.That is, no matter be a cube crystalline substance, or rhombohedral crystal, importantly, unifiedly be a kind of system of crystallization, and the crystal orientation of 90 ° of magnetic domains and the 180 ° of magnetic domains direction of all reversing simultaneously at identical voltage.That is, importantly design magnetic domain.

On the other hand, in the purposes of ferroelectric condenser so far, nearly all use Pt (111) and Ir (111) as electrode material, the PZT of use also easily is oriented in (111), is oriented in the PZT of (111), and apply flexibly magnetic domain effectively be cube brilliant PZT.On the other hand, the reliability of cube brilliant PZT is low.

Promptly, cube brilliant PZT (zones that Ti content is many), leakage current increases, significantly the static mint-mark characteristic of deterioration (will write data once, after preserving certain hour under the environment of room temperature or heating, apply the axial shift amount of voltage on the P-V B-H loop of the data of reading) and the obvious deterioration of data retention characteristics (will write data once, after preserving certain hour under the environment of room temperature or heating, the axial shift amount of remnant polarization on the P-V B-H loop of the data of reading).

Non-patent literature 1:J.Cross, M.Fujiki, M.Tsukada, K.Matsuura, S.Otani, M.Tomotani, Y.Kataoka, Y.Kotaka and Y.Goto, Integ.Ferroelectrics, 25,265 (1999).

Non-patent literature 2:I.Stolichnov, A.Tagantsev, N.Setter, J.Cross andM.Tsukada, Appl.Phys.Lett., 74,3552 (1999).

Non-patent literature 3:T.Morimoto, O.Hidaka, Y.Yamakawa, O.Ariusumi, H.Kanaya, T.Iwamoto, Y.Kumura, I.Kunishima and A.Tanaka, Jpn.J.Appl.Phys., 39,2110 (2000).

Summary of the invention

The purpose of this invention is to provide a kind of ferroelectric film, it can obtain the high ferroelectric device of reliability.Another object of the present invention provides ferroelectric memory and the piezoelectric element that utilizes this ferroelectric film.

The present invention relates to a kind of ferroelectric film, it is by using ABO ₃The perovskite structure ferroelectric of expression constitutes, and it is characterized in that, comprises the Si as A position counterion on the A position ²⁺, Ge ²+ and Sn ²⁺In at least a, on the B position, comprise Nb as B position counterion ⁵⁺According to the present invention, because the covalent bond of Nb and O is strong, can effectively prevent oxygen defect, it is a factor of the ferroelectric reliability of decision perovskite structure.In addition, in the present invention, by in the perovskite structure ferroelectric, adding Nb and Si, can be in the B position Nb of solid solution capacity.

The present invention relates to a kind of ferroelectric film, it is by the ABO that uses that comprises oxygen ion defects ₃The perovskite structure ferroelectric of expression constitutes, and it is characterized in that, comprises the Si as A position counterion on the A position ²⁺, Ge ²⁺, and Sn ²⁺In at least a, on the B position, comprise Nb as B position counterion ⁵⁺, the valence mumber of described A position counterion and owing to add B position counterion the total of remaining whole B position valence mumber, smaller or equal to not enough valence mumber corresponding to described oxygen ion defects amount.According to the present invention since the stable valence mumber of Nb be+5, have valence mumber than B position ion many+valence mumber more than 1 valency.Therefore, in the present invention, can remain the defective that valence mumber prevents oxygen (2) ion with this.That is,, prevent the defective of oxonium ion, can use ABO with the Nb ion exchange B position ion that adds ₃The neutral charge of the perovskite structure of expression is set up.For example, use ABO ₃The perovskite structure ferroelectric of expression is that PZT is when being ferroelectric, the A position counterion of ferroelectric film+divalent and owing to add B position counterion the total (Nb addition * (+1 valency)) of remaining valence mumber+1 ((Nb:+5 valency)-(Ti:+4 valency)=(+1 valency)), smaller or equal to not enough valence mumber (oxygen ion defects amount * (divalent) corresponding to the oxygen ion defects amount.

According to ferroelectric film of the present invention, the amount of described oxygen ion defects for the ferroelectric stoichiometric ratio of described perovskite structure smaller or equal to 15 moles of %.

According to ferroelectric film of the present invention, the amount that ion is added in described A position for the ferroelectric stoichiometric ratio of described perovskite structure smaller or equal to 16 moles of %, the amount that ion is added in described B position for the ferroelectric stoichiometric ratio of described perovskite structure smaller or equal to 30 moles of %.

According to ferroelectric film of the present invention, described perovskite structure ferroelectric is the Pb that comprises as A position ion ²⁺, and comprise Zr as B position ion ⁴⁺And Ti ⁴⁺PZT be ferroelectric.

According to ferroelectric film of the present invention, described perovskite structure ferroelectric is by cube brilliant formation in (111) crystal orientation.

According to ferroelectric film of the present invention, described perovskite structure ferroelectric is made of the rhombohedral crystal in (001) crystal orientation.

The present invention goes for comprising the ferroelectric memory of above-mentioned ferroelectric film.

The present invention goes for comprising the piezoelectric device of above-mentioned ferroelectric film.

Description of drawings

Fig. 1 is the generalized section according to the ferroelectric condenser of this form of implementation.

Fig. 2 is that expression changes the addition of Si and the figure of the XRD figure case of the PT film made in 0mol%～20mol% scope.

Fig. 3 is that expression is the figure of XRD figure case of the PT film of 20mol% with the Si addition.

Fig. 4 is a configuration of surface of representing not add the PT film of Si.

Fig. 5 is that expression Si addition is the configuration of surface of the PT film of 2mol%.

Fig. 6 is that expression Si addition is the configuration of surface of the PT film of 4mol%.

Fig. 7 is that expression Si addition is the configuration of surface of the PT film of 12mol%.

Fig. 8 is that expression Si addition is the configuration of surface of the PT film of 14mol%.

Fig. 9 is that expression Si addition is the configuration of surface of the PT film of 16mol%.

Figure 10 is that expression Si addition is the configuration of surface of the PT film of 18mol%.

Figure 11 is that expression Si addition is the configuration of surface of the PT film of 20mol%.

Figure 12 is that expression is respectively the TEM picture that the PT film of 16mol% and 18mol% is observed to the Si addition.

Figure 13 is that expression Si addition is Raman's spectroscopy scheme of the PT film of 16mol%.

Figure 14 shows that addition with Si changes and result that the PT film made is analyzed with Raman's optical spectroscopy in 0mol%～20mol% scope.

Figure 15 is that expression Si addition is the figure of hysteresis characteristic of the PT film of 12mol%.

Figure 16 is that expression Si addition is the figure of hysteresis characteristic of the PT film of 14mol%.

Figure 17 is that expression Si addition is the figure of hysteresis characteristic of the PT film of 16mol%.

Figure 18 is that expression Si addition is the figure of hysteresis characteristic of the PT film of 18mol%.

Figure 19 is that expression Si addition is the figure of hysteresis characteristic of the PT film of 20mol%.

Figure 20 is that the expression thickness is the figure of hysteresis characteristic of the PT film of 60nm.

Figure 21 is that the expression thickness is the figure of hysteresis characteristic of the PT film of 120nm.

Figure 22 is that the expression thickness is the figure of hysteresis characteristic of the PT film of 240nm.

Figure 23 is Zr/Ti than being 30/70 and the configuration of surface figure of 20/80 o'clock PZT film.

Figure 24 is Zr/Ti than being 30/70 and the figure of the hysteresis characteristic of 20/80 o'clock PZT film.

Figure 25 is the leakage current characteristic figure of PZT film that adds the Si of 16mol%.

Figure 26 is the fatigue properties figure of PZT film that adds the Si of 16mol%.

Figure 27 is the static mint-mark performance plot of PZT film that adds the Si of 16mol%.

Figure 28 is that thickness is the SEM section picture of the PZT film of 60nm～240nm.

Figure 29 adds Si and the configuration of surface of the PZTN film made.

Figure 30 is that expression is added Si and PZTN film, the PZT film made and add Si and the figure of the XRD figure case of the PZTS film made.

Figure 31 is that expression is added Si and the figure of the SEM section picture of the PZTN film made.

Figure 32 is that the expression thickness is the hysteresis characteristic of the PZTN film of 100nm, 150nm, 200nm.

Figure 33 is the figure of the relation of expression Nb addition and hysteresis characteristic.

Figure 34 is the figure of the relation of expression Nb addition and leakage current characteristic.

Figure 35 is at PZT, PbSiO ₃Behind the Si of middle interpolation 16mol%, compare the figure of the leakage current characteristic of PZT and PZTN.

Figure 36 is at PZT, PbSiO ₃Behind the Si of middle interpolation 16mol%, compare the figure of the fatigue properties of PZT and PZTN.

Figure 37 is the figure of the static mint-mark characteristic of the PZTN film when keeping 272 hour datas under representing 125 ℃.

Figure 38 is the figure that is illustrated in the dynamic scribe characteristic of the PZTN film that carries out under 85 ℃ the isoperibol.

Figure 39 is the figure that is illustrated in the static mint-mark characteristic of the PZTN film that carries out under 150 ℃ the isoperibol.

Figure 40 is the figure that is illustrated in the static mint-mark characteristic of PZT (Zr/Ti=20/80) film that carries out under 150 ℃ the isoperibol.

Figure 41 is the figure that is illustrated in the static mint-mark characteristic of PZT (Zr/Ti=30/70) film that carries out under 150 ℃ the isoperibol.

Figure 42 is result's the figure of the secondary ion mass spectrometry (SIMS) of expression PZTN film.

Figure 43 is result's the figure of the secondary ion mass spectrometry (SIMS) of expression PZTN film.

Figure 44 is result's the figure of the secondary ion mass spectrometry (SIMS) of expression PZTN film.

Figure 45 is expression PTN (PbTi _1-XNb _XO ₃: the figure of Raman's spectrophotometric spectra X=0～0.3).

Figure 46 is that expression is called as A ₁The figure of the position at the peak of the vibration mode of B position ion cause (2TO) and the relation of Nb addition.

Figure 47 is expression PZT (Zr/Ti=40/60)/Pt/TiO _XThe figure of the TEM section picture of capacitor.

Figure 48 is expression PZTN (Zr/Ti/Nb=20/60/20)/Pt/TiO _XThe figure of the TEM section picture of capacitor.

Figure 49 is the figure of hysteresis characteristic that the capacitor of 0.8 μ m * 0.8 μ m is processed in expression.

Figure 50 is the figure of hysteresis characteristic that the capacitor of 1 μ m * 1 μ m is processed in expression.

Figure 51 is the figure of hysteresis characteristic that the capacitor of 2 μ m * 2 μ m is processed in expression.

Figure 52 is the figure of hysteresis characteristic that the capacitor of 3 μ m * 3 μ m is processed in expression.

Figure 53 is the figure of hysteresis characteristic that the capacitor of 5 μ m * 5 μ m is processed in expression.

Figure 54 is the figure of hysteresis characteristic that the capacitor of 10 μ m * 10 μ m is processed in expression.

Figure 55 is the figure of hysteresis characteristic that the capacitor of 20 μ m * 20 μ m is processed in expression.

Figure 56 is the figure of hysteresis characteristic that the capacitor of 50 μ m * 50 μ m is processed in expression.

Figure 57 is the figure of hysteresis characteristic that the capacitor of 100 μ m * 100 μ m is processed in expression.

Figure 58 is the figure of expression according to the first principle Simulation result.

Figure 59 is the figure of the hysteresis characteristic of expression PZTV (Zr/Ti/V=20/60/20), PZTW (Zr/Ti/V/W=20/70/10), PZTTa (Zr/Ti/Ta=20/60/20).

Figure 60 is the figure of the electronic state density of expression PZT and PZTN system.

Figure 61 is the structural representation of the passive matrix ferroelectric memory device of the invention process form.

Figure 62 is a routine memory cell array of the invention process form and the sectional view that peripheral circuit is integrated in same on-chip ferroelectric memory device jointly.

Figure 63 be the invention process model deformation example 1T1C sections electrical memory means sectional view with and circuit diagram.

Figure 64 is the exploded perspective view of the related recording head of the invention process form.

Figure 65 is the plane graph and the sectional view of the related recording head of the invention process form.

Figure 66 is the synoptic diagram of the layer structure of the related piezoelectric element of the invention process form.

Figure 67 is the synoptic diagram of the related routine inkjet recording device of the invention process form.

Embodiment

Following with reference to the description of drawings the preferred embodiment of the present invention.

1. ferroelectric film and the ferroelectric condenser that uses this film

Fig. 1 is 100 generalized sections of the ferroelectric condenser with ferroelectric film 101 according to form of implementation of the present invention.

As shown in Figure 1, ferroelectric condenser 100 is by using ABO ₃The ferroelectric film 101 that the ferroelectric of the perovskite structure of expression constitutes, first electrode 102 and second electrode 103 constitute.

First electrode 102 and second electrode 103 are that the composite material of principal component constitutes by the monomer of noble metals such as Pt, Ir, Ru or by above-mentioned noble metal.If the ferroelectric element of diffusion in first electrode 102 and second electrode 103, produce the composition deviation of the interface locations between electrode and the ferroelectric film 101 so, the square property reduction of hysteresis, therefore first electrode 102 and second electrode 103 need have the compactness of indiffusion ferroelectric element.In order to improve the compactness of first electrode 102 and second electrode 103, for example take to be dispersed in method in the noble metal electrode etc. with the method for the heavy gas blowing film forming of quality or the divided oxide of Y, La etc.

Ferroelectric film 101 is formed by the ferroelectric of PZT system, and the ferroelectric of this PZT system is made of the oxide that comprises Pb, Zr, Ti element.Particularly in this form of implementation, the characteristics of this ferroelectric film 101 are to have adopted Pb (Zr, Ti, the Nb) O of doping Nb in the Ti position (B position) ₃(PZTN).That is, in this form of implementation, Nb ⁵⁺Be added as Ti position counterion.

Nb compares size (ionic radius is approaching, and atomic radius is identical) much at one with Ti, weight is 2 times, even therefore because the interatomic collision that lattice vibration causes can not make atom come off from lattice easily yet.There is valence to stablize again,, also passes through Nb easily even come off such as Pb for+5 valencys ⁵⁺The Pb valency that compensation comes off and.In addition, when crystallization, even coming off of Pb taken place, with respect to the big O of the size that comes off, it is easier to enter the little Nb of size.

In addition, Nb also has+4 valencys, therefore can replace Ti fully ⁴⁺And in fact the covalent bond of Nb is very strong, therefore can think that Pb also is not easy to come off.(H.Miyazawa，E.Natori，S.Miyashita；Jpn.J.Appl.Phys.39(2000)5679)

So far, doping Nb carries out in the rhombohedral crystal zone that Zr enriches in PZT, and its amount is about 0.2～0.025mol% (J.Am.Ceram.Soc, 84 (2001) 902; Phys.Rev.Let, 83 (1999) 1347) few amount.The reason of Nb of can not mixing in a large number is, for example adds the Nb of 10mol%, and crystallized temperature just rises to more than 800 ℃ so.

Therefore, in the ferroelectric film 101 of this form of implementation, also added PbSiO ₃Silicate (Si ²⁺Ion).Can reduce the crystallization energy of PZTN thus.That is, PZTN during, also add PbSiO when adding Nb as the material of ferroelectric film 101 ₃Silicate reduces the crystallized temperature of PZTN.In addition, can not adopt silicate (Si ²⁺) and adopt bismuth germanate (Ge ²⁺) or also can add other and contain Sn ²⁺The compound of ion.That is, in this form of implementation, can be with Si ²⁺, Ge ²⁺, Sn ²⁺In at least a ion add as Pb position (A position) counterion.

In addition, in this form of implementation, in order to prevent coming off of Pb in the ferroelectric film 101, can consider to enumerate lanthanide series such as La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu as the candidate of these elements with the method for the above element replacement Pb of+3 valencys.

Below, an example that is applicable to according to the film build method of the PZTN ferroelectric film 101 of the ferroelectric condenser 100 of this form of implementation is described.

PZTN ferroelectric film 101 can obtain by the following method.At first prepare mixed solution, it is made of first material solution that comprises at least a element among Pb, Zr, Ti and the Nb～the 3rd material solution, then by methods such as heat treatments with the oxide crystallization in these mixed liquors.

First material solution can be, in order to form the PbZrO that Pb in the metallic element and Zr form that constitutes by PZTN ferroelectric phase ₃The perovskite crystallization is condensation polymer solution with the anhydrous state dissolving in n-butanols equal solvent.

Second material solution can be, in order to form the PbTiO that Pb in the metallic element and Ti form that constitutes by PZTN ferroelectric phase ₃The perovskite crystallization is condensation polymer solution with the anhydrous state dissolving in n-butanols equal solvent.

The 3rd material solution can be, in order to form the PbNbO that Pb in the metallic element and Nb form that constitutes by PZTN ferroelectric phase ₃The perovskite crystallization is condensation polymer solution with the anhydrous state dissolving in n-butanols equal solvent.

With the first above-mentioned material solution, second material solution and the 3rd material solution, for example form by PbZr _0.2Ti _0.8Nb _0.2O ₃During the ferroelectric film 101 that (PZTN) constitutes, with (first material solution): (second material solution): even the mixed of (the 3rd material solution)=2:6:2 directly this mixed solution crystallization, still needs high crystallization temperature when making PZTN ferroelectric film 101.That is to say, when mixing Nb, because the temperature of crystallization rises impossible crystallization in the temperature range of the formed element below 700 ℃ suddenly, therefore the above Nb of 5mol% not have as an alternative that the element of Ti used so far, and restriction use always is in the scope of additive.Moreover, never cross the PZT cube of crystalline substance that the content of Ti is Duoed than Zr content so far.This part fact is documented in list of references J.Am.Ceram.Soc, and 84 (2001) 902 and Phys.Rev.Let, in 83 (1999) 1347 grades.

So, be to address the above problem in this form of implementation by following method.With the 4th material solution with more than the 1mol% but the concentration of not enough 5mol% add in the above-mentioned mixed solution, the 4th material solution is, in order to form PbSiO ₃Crystallization is condensation polymer solution with the anhydrous state dissolving in n-butanols equal solvent.

That is to say,, the crystallization temperature of PZTN can be controlled in 700 ℃ of following temperature ranges that can form element, and carry out crystallization by using the mixed solution of above-mentioned first solution, second solution, the 3rd solution and the 4th solution.

Particularly, mixed solution application step-remove ethanol step-dry heat treatment step-a series of steps such as degreasing heat treatment step are carried out necessary number of times after, burn till the back by the recrystallization annealing temperature process and form ferroelectric film 101.

The following describes the example of the condition of each step.

At first on the Si substrate, cover electrode noble metal film forming lower electrodes such as Pt.Secondly carry out the coating of mixed liquor with the method for spin coating.Particularly, on Pt covering substrate, drip mixed solution.Be rotated with about 500rpm and make the solution that is dripped fully under way on substrate, then revolution is dropped to the rotation of back below the 50rpm about 10 seconds.The dry heat treatment step carries out at 150 ℃～180 ℃.The dry heat treatment step carries out with electric furnace etc. under atmospheric environment.Equally, the degreasing heat treatment step is on temperature remains 300 ℃～350 ℃ electric furnace, carries out under atmospheric environment.The step of burning till of crystallization is to be undertaken by rapid thermal annealing methods such as (RTA) under oxygen atmosphere.

Also have, the thickness behind the sintering is about 100～200nm.Secondly, behind formation first electrodes such as sputtering method, the crystal property that forms and improve ferroelectric thin film with the interface of second electrode and ferroelectric thin film is a purpose, equally when burning till carries out post annealed with RTA etc. under oxygen atmosphere, forms ferroelectric condenser 100.

Embodiment 1

PbTiO for 1mol ₃, added as PbSiO ₃Si 20mol% below.Below, the Si that is carried is meant as PbSiO herein ₃And the Si that adds.In the present embodiment, the Si that is added in the perovskite structure ferroelectric is with SiO anything but ₂Form is added.And,, that is to say direct interpolation SiO if when adding the alcoxide of TEOS or Si ₂The time, SiO at first ₂Cover the Pt electrode surface, can not obtain the perovskite crystallization.

In the present embodiment, made the PbTiO that adds Si with the condition of table 1 ₃Film.Moreover, in following embodiment, do not add PbSiO ₃The time simply be expressed as PT or SO, the addition of Si is expressed as S2 during for 2mol%.

[table 1]

The XRD figure case of the sample that obtains in the present embodiment is shown in Fig. 2 and Fig. 3 (A), (B).Fig. 2 is that the addition with Si changes and figure that the XRD figure case of the PT film made is represented with longitudinal axis logarithm in 0mol%～20mol% scope.Fig. 3 (A), (B) are to be the figure that the XRD figure case of the PT film of 20mol% is represented with longitudinal axis logarithm with the Si addition.

According to Fig. 2, can confirm that all PT films all are that perovskite is single-phase.Also with good grounds Fig. 3 (A), (B) can also confirm that the PT film is (111) the single-orientated film that does not almost have out-phase.

In addition, Fig. 4～Figure 11 is the configuration of surface of expression according to the PT film of present embodiment acquisition.As Fig. 4～shown in Figure 11, along with the interpolation of Si, the particle diameter of PT crystallization becomes small.Particularly shown in S16 is very good flatness, but S18 that is to say later on when the Si addition surpasses 18mol%, can confirm the out-phase on surface.Do not confirm out-phase in the XRD figure case that in Fig. 2, shows, therefore can infer that out-phase is non-crystalline phase.

So to the PT film of present embodiment, be the sample S16 of 16mol% and the sample S20 of 18mol% with TEM picture comparison Si addition, its result is shown in Figure 12 (A), (B).From Figure 12 (A) as can be seen, in sample S16 and the interface portion between the Pt electrode do not have out-phase yet, be good perovskite crystalline phase.But from Figure 12 (B), as can be seen, in sample S20, be not only the surface, and the interface portion between the Pt electrode also is non-crystalline phase.

In addition, the PT film of sample S16 is analyzed by Raman's optical spectroscopy, Figure 13 is its Raman's spectroscopy scheme.As shown in figure 13, with according to the analysis result of XRD figure case and according to TEM as observed result, only confirmed the vibration mode of perovskite phase.

In addition, Figure 14 shows the result who the whole PT films that obtain is in the present embodiment analyzed by Raman's optical spectroscopy.As shown in figure 14, along with increasing of the addition of Si, the peak of vibration mode that expression is referred to as the A position ion of E (1TO) is shifted, and is referred to as A ₁Can't see fully in the vibration mode of B position ion (2TO) and change, Si becomes Si ²⁺, and part is replaced the Pb of A position.Yet after S18, the peak-shift of A position vibration mode is little, and the above Si of 16mol% changes inoperative to the A position.Therefore, can think that be identified noncrystalline is SiO mutually in the PT of present embodiment film ₂

Figure 15～Figure 19 is the figure of the hysteresis characteristic of the film that to estimate produced as stated above thickness be 240nm.As Figure 15～shown in Figure 19, when in the ferroelectric of perovskite structure, adding Si, suppress leakage current when improving configuration of surface, the Si addition obtains best B-H loop during for 16mol%.In addition, as Figure 18 and shown in Figure 19, if the Si addition surpasses 18mol%, so because the SiO that occurs in the interface ₂Influence, electric field can not be applied in the ferroelectric part fully, will appear at the tendency that remnant polarization value diminishes in the hysteresis characteristic like this.That is, by present embodiment clear and definite at PT etc. by ABO ₃The silicate amount of adding in the ferroelectric of the perovskite structure of expression is preferably 16mol%.Moreover if to be 16mol% convert with atom % (at%) is 13.7 atom % with the Si addition, all Si are as Si ²⁺Replace the A position.In addition, when the Si addition is 16mol%,, therefore can obtain good hysteresis characteristic because leakage current density is suppressed.

Addition with Si is fixed as 13.7at% then, forms the PT film with different thickness, and the new filming of ferroelectric film is studied.Figure 20～Figure 22 shows the hysteresis characteristic of this research.It is that to show thickness be that 120nm, Figure 22 show the situation that thickness is 240nm for 60nm, Figure 21 that Figure 20 shows thickness.From Figure 20～Figure 22 as can be seen, thickness is can obtain good magnetic hysteresis effect in the scope of 60nm～240nm, adds Si at PT and helps to improve leakage current characteristic.

Secondly, utilize the Si addition 13.7at% (16mol%) that obtains in the test that the PT film is carried out, with PT equally with ABO ₃Add Si among the ferroelectric PZT of the perovskite structure of expression.Figure 23 (A), (B) show the configuration of surface of the PZT film that at this moment obtains.Figure 23 (A) be Zr/Ti than the configuration of surface figure that is 30/70 o'clock PZT film, Figure 23 (B) is that Zr/Ti is than the configuration of surface figure that is 20/80 o'clock PZT film.In addition, Figure 24 (A), (B) show the hysteresis characteristic of the PZT film that at this moment obtains.Figure 24 (A) be Zr/Ti than the hysteresis characteristic figure that is 30/70 o'clock PZT film, Figure 24 (B) is that Zr/Ti is than the hysteresis characteristic figure that is 20/80 o'clock PZT film.As Figure 23 and shown in Figure 24, also can obtain surface of good form and hysteresis characteristic at the PZT film.

Secondly, Figure 25～27 show in the result who aspect the Chemical Calculation composition PZT film that has added 16mol% (13.7at%) Si has been carried out obtaining behind the reliability evaluation (leakage current characteristic, fatigue properties, static mint-mark characteristic).Figure 25 is leakage current characteristic figure, and Figure 26 is fatigue properties figure, and Figure 27 is static mint-mark performance plot.According to Figure 25～Figure 27 as can be seen, the PZT film of present embodiment is shown as low-down reliability.For example, though leakage current characteristic when not adding Si relatively, reduced about 10 times leakage current, along with the increase leakage current of Ti content also increases, therefore the effect that reduces leakage current by interpolation Si is not very desirable.Fatigue properties too, though along with the raising that is added with a little of Si, but very undesirable.Particularly there is not effect fully for the mint-mark characteristic.

So to the PZT film analysis of present embodiment SEM section picture, its result is shown in Figure 28 (A)～Figure 28 (C).From Figure 28 (A)～Figure 28 (C) as can be seen, the PZT film that has added Si is not the column structure of common PZT film, but has formed granular texture.Therefore, can infer and form the structure that many capacitances in series couple together at direction of an electric field, though so effect has been arranged aspect the leakage current improving, the existence on many grains circles has become the reason of interfacial polarization, makes fatigue properties and mint-mark characteristic degradation.

As mentioned above,, can improve leakage current a little by in being rich in cube brilliant PZT of Ti, adding silicate, but to not improvement effects such as big fatigue properties of the reliability correlation of FeRAM and mint-mark characteristic, therefore need an improvement method.

Embodiment 2

By embodiment 1 clear and definite in being rich in the PZT of Ti, add Si effect be not very desirable to the reliability of guaranteeing equipment.But highly integrated for the ferroelectric internal memory still need be rich in the cube crystalline membrane (cube brilliant film) of Ti.That is, improve anti-electric field action by the square property that is rich in the effect of Ti raising magnetic hysteresis, anti-structure of crosstalking in the time of filming can being designed thus.In addition, because relative dielectric constant is reduced to about 300 from 1500, therefore can realize high speed motion.

So, be basic Chu with cube (cube crystalline substance) PZT in the present embodiment, by among the present invention with ABO ₃The method of adding ion in the B position in the perovskite structure ferroelectric of expression realizes good magnetic hysteresis effect and high reliability simultaneously.

At first, argumentation is about the problem of PZT ferroelectric material.The leakage current density problem of PZT was not much accounted of in the past, this be because during reading of data with the above impulse electric field of several MHz, so can ignore the influence of leakage current.If but we think that there is its reason in PZT material itself, when having increased the situation of leakage current density thus, the leakage current increase is a very large problem for ferroelectric material.So the present invention is the leakage current that reduces cube brilliant PZT that purpose is studied.

At first, discussed just electric leakage of PZT ferroelectric material itself to the leakage current density cause of increased, will be more serious if increase the content electric leakage of Ti.Secondly, if think what oxygen defect caused, in the perovskite structure, the cationic oxonium ion that always exists on every side, therefore cationic defective will become fixed charge, be not easy to be moved.On the other hand, oxonium ion is being connected in the crystal structure of perovskite from top to bottom, therefore can think that oxygen defect works to leakage current.In addition, usually PZT ferroelectric material and the Bi bedded structure ferroelectric material density of comparing leakage current is higher, and along with the density of the increase leakage current of Ti also increases.Can infer also that from these Pb and Ti also are the leakage current cause of increased.

Table 2 is summaries that PZT constitutes the various physical property values of element.

[table 2]

Plumbous vapour pressure height become the steam start vaporizer about 150 ℃, and the binding energy with oxygen is very little as can be seen from Table 2, is 39kcal/mol.That is, can infer, if generally implement the crystallization heat treatment below 700 ℃, so because the heat energy that applies during this crystallization heat treatment and the Pb-O key is cut off forms the Pb defective in order to make the PZT crystallization.Then, because the defective of Pb according to the neutral charge principle, produces the defective of O.

On the other hand, can know the atomic weight minimum of Ti in PZT formation element by table 2, be 47.87.Each atom that constitutes crystallization here often repeatedly is rotated and collides.Each atom particularly often repeatedly vibrates, rotates and run foul of each other according to temperature according to the environment at own place.Say nothing of when carrying out crystallization heat treatment, each atom is repeated collision more intensely.At this moment, the lightest the easiest influence that is collided of Ti.That is to say, can infer that Ti is also with the equally easy generation defective of Pb.Therefore, during crystallization heat treatment, might be cut off, generate the Ti defective according to the heat energy Ti-O key that applies.If owing to oxygen defect takes place the neutral charge principle, Schottky defect (defective that cation and anion generate in pairs) takes place easily among the so so-called cube of brilliant PZT when generating the Ti defective, causes that owing to Schottky defect the density of leakage current increases.

If the leakage current density increase pattern of cube brilliant PZT that discusses is above set up, these problems only are difficult to be resolved in PZT so.Because according to table 2, be difficult to control evaporation and the defective of Pb.If like this, under the situation that allows the Pb defective, even as long as the Pb defective has taken place, and oxygen defect does not take place yet, thereby it is just passable not increase leakage current density so.

So, attempted in the present embodiment with ABO ₃In the ferroelectric material of the perovskite structure of expression, the method for mixing up the Nb ion in the B position of existing for the Ti ion.That is, the Ti ion of B position that will equally form defective with Pb so just can reduce the content of Ti with a Nb displacement part.

Secondly, the reason of selecting Nb as the interpolation ion of B position is described.The size of Nb atom and Ti much at one, weight just in time is 2 times, the influence that therefore is subjected to atomic collision is smaller.And, consider that from energy point of view it is easier than big oxygen atom generation defective to add little Nb.In addition, the stable valence mumber of Nb is+5, than Ti+4 valencys are many+1 valency.One of characteristics of the present invention are used for this unnecessary+1 valency the defective of anti-block (divalent) ion.That is to say,, can prevent the defective of an oxonium ion like this, keep neutral charge thus with two Nb ion exchange Ti ions.In addition, according to first principle simulation, the covalent bond of Nb and oxygen is very strong, because Nb is displaced to the B position, so oxygen itself becomes and is difficult to produce defective.(list of references 1:H.Miyazawa, E.Natori, S.Miyashita, T.Shimoda, F.Ishii and T.Oguchi, Jpn.J.Appl.Phys.39,5679 (2000)).

The said here example that the Nb ion is doped to PZT was also attempted in the past, but nearly all thought and mix up very difficulty of Nb.(list of references 2:T.Matsuzaki and H.Funakubo, J.Appl.Phys.86,4559 (1999), list of references 3:G.Bums andB.A.Scott, Phys.Rev.Lett., 25,1191 (1970).

Representational example is to use vapour deposition process (MOCVD) PbTiO ₃When the Ti ion (PT) is used Nb ion exchange 2.3at%, can obtain single calcium titanium ore bed, but not report big characteristic variations.And the reason of adding Nb in the past is in order to offset the Pb defective that PZT takes place by the superfluous valency of Nb.But,, so also the electrical leakage quantity cause of increased can't be described if the Pb defective is envisioned for fixed charge.In addition, in list of references 3, proposed when adding the Nb of 5at%, can produce the burnt green stone phase of normal dielectric, the difficulty of mixing up Nb still has been described.

Be that the basis is studied with PZT (Zr/Ti=20/80) in the present embodiment, the result is for existing the oxygen defect more than the 10at% among the PZT that makes under the condition of present embodiment.Promptly, if the PT and the PZT in the present embodiment of report have equal oxygen defect in the list of references 3, can only improve the oxygen defect of half amount that is same as the Nb addition when adding the Nb of 2.3at% so, that is to say only has 1.15at%, and can think does not have much effects.In addition, mocvd method is can directly obtain solid-state method from gaseous state, gas becomes solid state needs big energy changing, although be an effectively one-tenth embrane method aspect the effect that reduces crystallized temperature therefore, but, be that the interpolation owing to Nb is significantly risen the crystallized temperature of PZT from obtaining the Jiao Lvshi of cold state.

Then, if there is the above oxygen defect of 10at% in PZT, in order to reach the oxygen defect purpose that prevents PZT, need the Nb addition about 20at% so.But, also must consider to reduce crystallized temperature simultaneously.So in present embodiment 1, represented to replace the A position, also can be improved as configuration of surface fine and close level and smooth with minute quantity thus with Si.

According to above result of study, in the present embodiment, having added concentration when adding Nb is the following minute quantity Si of 5at%, and does not add a large amount of Si that can destroy the PZT column structure as embodiment 1.Condition with table 3 forms the PZT film.

[table 3]

Adopt method of spin coating in the present embodiment, add Nb and Si in advance in order to the sol-gel solution that forms PZT, making thickness under 650～800 ℃ oxygen atmosphere is PZTN (Pb/Zr/Ti/Nb=110/20/60/20) film of 200nm.Ferroelectric film is to form on electrode, and electrode material is Pt.

Figure 29 (A)～figure (C) shows the ferroelectric film configuration of surface that obtains.Figure 30 (A)～Figure 30 (C) shows the XRD figure case of each ferroelectric film.If do not add Si (Figure 29 (A), Figure 30 (A)) fully, when burning till, 800 ℃ high temperature only have the burnt green stone attitude of normal dielectric.Secondly, add the Si (Figure 29 (B), Figure 30 (B)) of 0.5mol%, under 650 ℃ of firing temperatures, have the burnt green phase of normal dielectric, but also observe the peak that reflects mutually from perovskite.In addition, when the Si addition is 1mol% (Figure 29 (C), Figure 30 (C)), under 650 ℃, obtain the perovskite simple layer, have the surface of good form simultaneously.

In addition, as the SEM section picture that shows among Figure 31 (A)～(C), the PZTN film that obtains in the present embodiment keeps the distinctive prismatical structure of PZT ferroelectric film, compares with the film of the interpolation silicate of embodiment 1, and membrane structure is different fully.

Form 100 μ m φ-Pt upper electrodes with gunite on the 200nm-PZTN film that obtains in the present embodiment, estimate electrical characteristics then, shown in Figure 32 (A)～Figure 32 (C), its result obtains to have the P-E hysteresis characteristic of good square property.For example, when the thickness shown in Figure 32 (C) is 200nm, can clear and definite amount of polarization Pr be about 35 μ C/cm ², anti-electric field Ec is that (magnetic hysteresis is polarized to 0 during for ± 1.6v to 80kv/cm, so Ec=1.6v/200nm=80kv/cm ²) the ferroelectric characteristic.Even it is emphasized that to have good square property, have the big anti-electric field of 80kv/cm again, but at the electric field of 100kv/cm, ferroelectric hysteresis is almost saturated.

Figure 33 (A)～Figure 33 (D) is the graph of a relation of expression Nb addition and hysteresis characteristic.Figure 33 (A) is that the Nb addition is the situation of 0 (at%), and Figure 33 (B) is that the Nb addition is the situation of 5 (at%), and Figure 33 (C) is that the Nb addition is the situation of 10 (at%), and Figure 33 (D) is that the Nb addition is the situation of 20 (at%).Figure 34 is the graph of a relation of Nb addition and leakage current characteristic.Show that as Figure 33 (A) when the Nb addition was 0at%, when that is to say conventional PZT, leakage current characteristic was bad, shown in the zero seal part of the dotted line among the figure, owing to contain a large amount of leakage currents, so magnetic hysteresis top sticks out.As shown in figure 34, when the Nb addition was 5at%, although leakage current characteristic is enhanced, shown in the zero seal part of the dotted line among the figure, ohm circuit part still existed, and it is not very desirable improving.Shown in Figure 33 (B), the Nb addition when being 5at% square property be not fine, and saturation characteristic neither be fine, therefore is difficult to use low voltage driving device.

In addition, shown in Figure 33 (C), (D), when the Nb addition is 10at% and 20at%, can obtain having the extraordinary hysteresis characteristic of caryogram of good saturation characteristic, as shown in figure 34, ohm galvanic areas is also significantly improved in the leakage current characteristic.When the Nb addition was 20at%, shown in Figure 33 (D), because 20at% is arrived in the displacement of the B position ion of decision ferroelectric characteristic more, high voltage rose near 1.6%, but in the following scope of 2v by saturated.This saturation characteristic is the maximum characteristic of PZTN ferroelectric material.The above fact can illustrate because the oxygen defect of PZT surpasses 10%, and the addition of Nb need reach 20at%, minimumly also will add 10at%.

Figure 35 is to be PZT and the PbSiO of 200nm at thickness ₃Behind the middle interpolation Sil6mol%, compare the figure as a result of the leakage current characteristic of PZT and PZTN.According to Figure 35, PZT also increases along with strengthening the voltage leakage current density, but in adding on a large scale, the low-voltage of PZTN below 5v almost can't see the increase of leakage current density, even emit the electric current structure division at so-called Schottky, voltage more than 5v adds significantly, the increase of leakage current density is arranged, but the grade of relatively leaking with PZT still is low.This is because the oxygen defect density difference between PZT and the PZTN, and the leakage current part is emitted the voltage that part that current segment moves to leakage current and increase is gone from Schottky, is different causes in PZT and PZTN.As its result, can see that (under the 1.8v～3v), PZTN lowers about about 4 figure places than the leakage current density of PZT, can also confirm that PZTN and PZT relatively, have about 10000 times insulating properties for working voltage at this film.

Secondly, the figure of expression fatigue properties is Figure 36.The ferroelectric condenser of use in characteristic measurement is that upper electrode or lower electrode all use Pt, as pure ferroelectric material its characteristic compared.If use the Pt electrode, general PZT is with 10 ⁹Till cycle degradation is reduced to below half to amount of polarization.In the past, the PZT material was easy to fatigue on the Pt electrode, but the result in this example is not for being PZT fatigue, but had hinted that the PZT of oxygen defect is degenerating.Like this, the present invention is remarkable to be to beginning just to exist the improvement of PZT in the past, and is the invention about new material fully.

Then, the evaluation result of mint-mark characteristic and data retention characteristics is described, assay method is with reference to list of references 4,5.(list of references 4; J.Lee, R.Ramesh, V.Karamidas, W.Warren, G.Pike and J.Evans., Appl.Phys.Lett., 66,1337 (1995), list of references 5; A.M.Bratkovsky and A.P.Lebanyuk.Phys.Rev.Lett., 84,3177 (2000)).

Figure 37 is the maintenance/static mint-mark evaluating characteristics result when under 125 ℃ data having been kept 272 hours.In addition, Figure 38 be under 85 ℃ isoperibol, carry out 10 ⁸Dynamic scribe characteristic during the mint-mark in cycle.According to Figure 38, the axial amount of movement of voltage of the hysteresis curve after the observation mint-mark, PZTN obviously reduces than the amount of movement that PZT obtains as can be seen.

Then, under 150 ℃ hot environment, carried out the evaluation test of static mint-mark characteristic, its result such as Figure 39～Figure 41.Figure 39 is, about the result of the PZTN film of present embodiment.Figure 40 is the result of relevant PZT (Zr/Ti=20/80) film.Figure 41 is the result of relevant PZT (Zr/Ti=30/70) film.For PZT, lose 40% amount of polarization when reading, but the situation of PZTN, the amount of polarization that reads does not almost change.The two difference mainly is the difference of the static mint-mark characteristic of PZT and PZTN.That is,, only be identified good mint-mark characteristic at Figure 39 PZTN film according to Figure 39～Figure 41.

As mentioned above, PZTN compares with PZT and has quite high reliability.

In the present embodiment for the high reliability of the PZTN material confirming to obtain expecting, whether with prevent that oxygen defect is relevant, and carried out various analyses.At first, adopt secondary ion mass spectrometry (SIMS) to investigate the oxygen defect amount, its result such as Figure 42～Figure 44.Solid line is PZTN in each figure, and dotted line is the situation of PZT.PZTN by Figure 44 and PZT learn that the oxygen concentration of PZTN is high by about 10% after relatively, and this can think can suppress the proof of the effect of oxygen defect to adding Nb.Simultaneously, confirmed again that by Figure 43 Ti ion concentration PZT is low by about 10%, this few 10% is exactly to be replaced that part of getting off by Nb.

Here, SIMS is because the mensuration sensitivity of Nb is not very high cause, employing induced plasma emission spectrum method (ICP) and x-ray photoelectron spectroscopy (XPS) have carried out the mensuration to Nb concentration, it the results are shown in Table 4, table 5, can be clearly be about 20at% about the Nb concentration of the B position among the PZTN (Zr, Ti, Nb).

[table 4]

XPS	Unit	Pb-4f	Zr-3d	Ti-2p	Nd-3d	O-ls	Si-sp	Total
XPS	Unit	Pb-4f	Zr-3d	Ti-2p	Nd-3d	O-ls	Si-sp	Total	PZT	Atomic％	24.8	5.7	21.0	-	48.4	0.1	100
PZTN	Atomic％	24.4	5.7	15.3	5.7	48.8	0.1	100	PZT	Atomic％	24.8	5.7	21.0	-	48.4	0.1	100

[table 5]

Afterwards, with Raman's optical spectroscopy whether Nb being displaced to the B position analyzes.Figure 45 shows the PTN (PbTi when changing doping _1-XNb _XO ₃: Raman's spectrophotometric spectra X=0～0.3).

Expression as shown in figure 45 is called as A ₁The peak of the vibration mode of B position ion cause (2TO) is displaced to the lower wave number side simultaneously with the increase of the Nb doping shown in Figure 46 (A), and this expression Nb is displaced to the B position.In addition, expression PZTN (PbZr _YTi _1-Y-XNb _XO ₃: among Figure 46 X=0～0.1) (B), can confirm that also Nb is displaced to the B position.From above-mentioned result of study, the reason that the PZTN material among the present invention has good characteristic is that the Nb of the 20at% that the B position in PZT imports compares with simple PZT, prevents the oxygen defect of 10at%.In the present embodiment, add the Si of minute quantity, the reason of a large amount of Nb that just can mix is that Si has the effect that reduces crystallized temperature, and can make the Nb solid solution.

Secondly, Figure 47 and 48 shows and uses dry ecthing method, the actual TEM section picture that is processed into the capacitor of 10 μ m * 10 μ m.Figure 47 is PZT (Zr/Ti=40/60)/Pt/TiO _XThe observed result of capacitor, Figure 48 is PZTN (Zr/Ti/Nb=20/60/20)/Pt/TiO _XThe observed result of capacitor.Carry out etching, the two end portions of PZT that cuts off and PZTN may be rotten and contrast (contrast) that cause has white coming off, and can confirm that in PZT near the etching length is that the contrast of 1～1.5 μ m comes off, and, can confirm to come off with the contrast at whole interfaces of top Pt electrode.In addition, measure the film of this part and form, confirmed that Pb forms significantly minimizing.On the other hand, in PZTN, have only the two end portions of processing to exist contrast to come off, analyze the composition of the neighbouring part at two ends, do not find coming off of Pb fully.Carry out the composition analysis of middle body simultaneously, do not find coming off of Pb equally fully.As mentioned above, it is destructive that PZTN ferroelectric according to the present invention has the anti-processing that can't imagine with general knowledge so far.

Therefore, estimated the hysteresis characteristic of the capacitor that is processed into 0.8 μ m * 0.8 μ m～100 μ m * 100 μ m respectively, shown in Figure 49～57, obtained almost and the incoherent hysteresis characteristic of size.This also is to explain with former general knowledge, is the new features that are suitable for PZTN of the present invention.

Embodiment 3

In the present embodiment, illustrate as the B position and change the reason that material is selected Nb especially.

From the first principle analog result of Figure 58 also as can be seen, the covalent bond of Nb and O is strong.And in order to prevent oxygen defect effectively, the power that need combine with oxygen is that covalent bond is strong.Therefore, in the present embodiment, utilize Ta, V and W, replace the research of Nb.

Ta and V be+5 valencys, and be same with Nb, made the PbZr of the Ti of displacement 20at% _0.2Ti _0.6Ta _0.2O ₃And PbZr _0.2Ti _0.6V _0.2O ₃Because W+6 valencys, therefore, made the PbZr of the Ti of displacement 10at% _0.2Ti _0.7W _0.1O ₃Pb surplus, firing condition and other conditions are identical with table 3.

Its result has obtained the hysteresis characteristic shown in Figure 59 (A)～59 (C).The situation of Figure 59 (A) expression PZTV (Zr/Ti/V=20/60/20), the situation of Figure 59 (B) expression PZTW (Zr/Ti/V/W=20/70/10), the situation of Figure 59 (C) expression PZTTa (Zr/Ti/Ta=20/60/20).The V that Figure 59 (A), (B) illustrate, the situation of W and since with the covalent bond of oxygen a little less than, therefore show and leak the bad hysteresis characteristic of square property than Nb.On the other hand, the situation of Ta, under the firing condition of table 3, hysteresis characteristic is bad.And, burn till at 850 ℃, shown in Figure 59 (C), obtain magnetic hysteresis preferably.But, there is not Nb good, relatively, crystallized temperature rises, and is difficult to be applicable to element during with interpolation Nb.As mentioned above, also can confirm the first principle result of calculation of Figure 58 from result of the test.

Then, calculate the reason that investigation PZTN material has very high insulating properties from first principle.The migration metal oxide is made of the crystallization of ions binding substantially.But,,, move the metal track and play important effect near the covalent bond between the oxygen 2p track from the detailed explanation of position that first principle is calculated for its ferroelectric mechanism that manifests.The migration metal track energy of state of atom and the difference of oxygen 2p track energy are more little, and its covalent bond is strong more, and ferroelectricity strengthens.

On the other hand, by ABO ₃In the migration metallic compound that perovskite structure constitutes, when entering Pb or Bi in the A position, the 6p track of Pb and Bi and its are near generating new covalent bond between the oxygen 2p track, and with the covalent bond of B position migration metal, ferroelectricity strengthens.This may be the high Curie temperature among PZT or the BIT and the reason of big polarization torque.At this, calculate the electronic state of research PZT system and the relation of high-insulativity with first principle.Suppose that crystalline texture is the super cell of (2 * 2 * 2).

Figure 60 (A)～Figure 60 (E) shows the electronic state density of PZT and PZTN system.Figure 60 (A) is the Pb (Zr that does not have defective _0.25Ti _0.75) O ₃State density.The top of valence band is made of the 2p track of oxygen.In addition, the bottom of conduction band is made of the d track of migration metal, particularly Ti.Situation when Figure 60 (B) expression replaces with Nb with the Ti of the B position 25% of PZT.Observe the position of Fermi level, just can know and mix up electronics in the conduction band.And its amount of mixing up is just in time Duoed one 5 valence electrons corresponding to Nb than Ti and is offered the ion that is and retouch picture.Situation when Figure 60 (C) represents the Pb defective 12.5% of PZT.Can know that equally the hole is mixed up at valence band.Its hole amount of mixing up is the amount of the valence electron that loses corresponding to the Pb as 2+ ion vibration from be.Figure 60 (D) expression replaces with Nb with the Ti of B position 25%, simultaneously the situation during Pb defective 12.5%.Cancel each other in electronics that is mixed up and hole respectively, and Fermi surface disappears, and insulating properties is resumed.Relatively Figure 28 (A) and Figure 60 (D), the electronic structure near the band gap is observed more similarly from state density, in the operation of Figure 60 (D), may be the electronic state (variation of rigid strip) that does not destroy original PZT.

At this, for the B position replacement amount δ of Nb,, be necessary the Pb that defective is limited in order to keep the insulator that is, its defect level is necessary for δ/2.Figure 60 (D) is corresponding to the electronic state of PZTN system.On the other hand, Figure 60 (E) is for PZT, and Pb and the oxygen that is adjacent is the state density of (Schottky defect) during defective 12.5% in couples.Band gap is opened, but the state of impurity energy level occurs thinking in the bottom of conduction band.Therefore, band gap declines to a great extent for Figure 60 (A).For the band gap of Figure 60 (A), Figure 60 (D) decline 0.2eV of PZTN system is though have identical defect level, Figure 60 (E) decline 1.2eV.Declining to a great extent of band gap among Figure 60 (E) owing to oxygen defect causes.This is because the electrostatic potential of migration metal track, original adjacent positro cloud be because oxygen defect and being lost, thereby descend.The insulation characterisitic of system is by the size decision of band gap.But the band gap of insulator extensively is the necessary condition of good insulator.Therefore, the high reason of insulating properties is that oxygen defect is few, the decline of band gap is little causes in PZTN system.And the bad reason of the insulating properties of existing P ZT is, there is the Schottky defect of Pb-O in a large number in stoichiometry (chemical equivalent composition), therefore, can infer, band gap reduces shown in Figure 60 (E), wears the decline of skew at sector electrode.

The summary of embodiment 1～3

Only add about 1% minute quantity Si when adding Nb, can be to the Nb more than the B position solid solution 20at% among the PZT.Si has the function of solid solution Nb.

100nm～200nm-PZTN film shows the good hysteresis characteristic of square property, and leakage current density is 10 ^-8A/cm ²Below, have existing 1000～10000 times of insulating properties, and, have good reliability.

Analyzing film is formed, and the PZT comparison with simple reduces by 10% oxygen defect.

2. ferroelectric memory

Figure 61 (A) and Figure 61 (B) are the structural representation at the passive matrix ferroelectric memory device 300 of the invention process form.Figure 61 (A) is its plane graph, and Figure 61 (B) is the sectional view along the A-A line of Figure 61 (A).Ferroelectric memory device 300 shown in Figure 61 (A) and Figure 61 (B), has assortment and gives the bit line 304～306 of determined number for the word line 301～303 of determined number and assortment, and they all are formed on the substrate 308.Between word line 301～303 and bit line 304～306, inserted the ferroelectric film 307 that forms by the PZTN that in above-mentioned example, illustrates, and in the intersection region of word line 301～303 and bit line 304～306, formed ferroelectric condenser.

In assortment in the ferroelectric memory device 300 of the memory cell that constitutes by this simple matrix, writing and reading of ferroelectric condenser in the intersection region that is formed on word line 301～303 and bit line 304～306 is to carry out with reading with (claiming that this is " peripheral circuit ") such as amplifying circuits by not shown peripheral driving circuit.This peripheral circuit, form by memory cell array and other on-chip MOS transistor, also can be connected word line 301～303 and bit line 304～306, perhaps, peripheral circuit and memory cell array are integrated on the same substrate by on substrate 308, using monocrystalline silicon substrate.

Figure 62 is the sectional view that a routine ferroelectric memory device 300 is shown, and this ferroelectric memory device 300 is in this example, and memory cell array and peripheral circuit are integrated on the same substrate jointly.

In Figure 62, on monocrystalline silicon substrate 401, formed MOS transistor 402, and this transistor formation region territory promptly becomes the peripheral circuit part.MOS transistor 402 is made of monocrystalline silicon substrate 401, source and drain areas 405, gate pole dielectric film 403 and gate electrode 404.

In addition, ferroelectric memory device 300 has element and separates with oxide-film 406, first interlayer dielectric 407, first wiring layer 408 and second interlayer dielectric 409.

In addition, ferroelectric memory device 300, has the memory cell array that constitutes by ferroelectric condenser 420, ferroelectric condenser 420, as the lower electrode (first electrode or second electrode) 410 of word line or bit line, comprise ferroelectric mutually with normal dielectric mutually ferroelectric film 411 and be formed on the ferroelectric film 411 and the upper electrode (second electrode or first electrode) 412 that becomes bit line or word line constitutes.

Also have, ferroelectric memory device 300 has the 3rd interlayer dielectric 413 on ferroelectric condenser 420, by second wiring layer 414 memory cell array partly is connected with peripheral circuit.In addition, in ferroelectric memory device 300, on the 3rd interlayer dielectric 413 and second wiring layer 414, formed diaphragm 415.

According to ferroelectric memory device 300, memory cell array and peripheral circuit can be partially integrated on the same substrate with above structure.In addition, ferroelectric memory device 300 shown in Figure 62, be the structure that on its peripheral circuit part, has formed memory cell array, but do not dispose memory cell array on the peripheral circuit part, and the memory cell array plane is connected in the structure of peripheral circuit part and also is fine.

Used ferroelectric condenser 420 in this example, the PZTN related by above-mentioned example constitutes, and therefore, rectangular hysteresis is very good, has stable noiseproof feature.Also have, this ferroelectric condenser 420 reduces the infringement to peripheral circuit etc. or other element by the low temperatureization of treatment temperature, in addition, has also reduced and has handled infringement (the particularly reduction of water element), therefore, can suppress the deterioration of the hysteresis that causes because of infringement.Thereby,, make the practicability of passive matrix ferroelectric memory device 300 become possibility by using ferroelectric condenser 420.

In addition, structural map as the 1T1C sections electrical memory means 500 of variation has been shown among Figure 63 (A).Figure 63 (B) is the equivalent circuit figure of ferroelectric memory device 500.

Ferroelectric memory device 500 shown in Figure 63 (A), (B), is the memory component with the DRAM structural similarity of being used transistor unit 507 (1T) to form by switch.This switch has capacitor 504 (1C) with transistor unit 507 (1T), and its ferroelectric ferroelectric film 503 of PZTN by lower electrode 501, the upper electrode 502 that is connected the anode line and suitable this example forms; Gate electrode 506, a side of source-drain electrode is connected on the data wire 505, thereby is connected on the word line.1T1C type memory, it writes and reads can be carrying out at a high speed below the 100ns, thereby and the data that write be difficult for losing and be expected to substitute SRAM etc.

3. piezoelectric element and ink jet recording head

Below, the ink jet recording head of the invention process form is elaborated.

Ink jet recording head, its part of pressure generating chamber that has been communicated with the nozzle opening of the ink droplet that spues is made of oscillating plate, and makes this oscillating plate distortion and to the ink pressurization of pressure generating chamber by piezoelectric element, thereby from the nozzle opening ink droplet that spues.In ink jet recording head, used piezoelectric actuator to the elongation of the direction of principal axis of piezoelectric element, the longitudinal vibration mode that shrinks; Used the piezoelectric actuator of beam mode to be practical for two kinds.

When using the transmission device of beam mode, for example, forming uniform piezoelectric body layer by film technique on the whole surface of oscillating plate, is shape corresponding to pressure generating chamber by the lithographic plate method with this piezoelectric body layer cutting, thereby independent by being arranged so that each pressure generating chamber.

Figure 64 is the exploded perspective view that the related ink jet recording head summary of an example of the present invention is shown, and Figure 65 is plane graph and the A-A ' sectional view of Figure 64, and Figure 66 is the synoptic diagram that the layer structure of piezoelectric element 700 is shown.As shown in the figure, stream forms substrate 10, and having formed thickness is the elastic membrane 50 of 1～2um, and it is formed by the silicon single crystal substrate of face orientation (110) in this example, forms silicon dioxide by thermal oxidation in advance on its one side.On stream formed substrate 10, a plurality of pressure generating chamber 12 was set up in parallel at its Width.In addition, form at stream on the zone in the long hand direction outside of pressure generating chamber 12 of substrate 10 and formed connected component 13, connected component 13 and each pressure generating chamber 12 are providing ink road 14 connections by being arranged on each pressure generating chamber 12.In addition, connected component 13, the envelope that is communicated with narration is in the back ended the reserve part 32 of substrate 30, thus formation is as the part of the reserve part 800 of the common ink chamber of each pressure generating chamber 12.Providing ink road 14 is formed by specific pressure generating chamber 12 narrower width, and will remain necessarily from the ink flow path impedance of connected component 13 feed pressure generating chamber 12.

In addition, form at stream on the opening surface side of substrate 10, fixed nozzle switch 20 by bonding agent or thermal weld film etc., be provided with on this nozzle switch connection with the end of the providing ink road 14 opposite sides of each pressure generating chamber 12 near nozzle opening 21.

On the other hand, forming on the opposite side of opening surface of substrate 10, as mentioned above, formed thickness and for example be about the elastic membrane 50 of 0.1um, and on this elastic membrane 50, be formed with the insulator film 55 that thickness for example is about 0.4um with this stream.On this insulator film 55, formation thickness for example is about the lower electrode film 60 of 0.2um, the piezoelectric body layer 70 that thickness for example is about 1.0um, the upper electrode film 80 that thickness for example is about 0.05um by technology described later is stacked.At this, piezoelectric element 700 refers to comprise the part of lower electrode film 60, piezoelectric body layer 70 and upper electrode film 80.Usually, with piezoelectric element 300 certain on one side electrode and another electrode and piezoelectric body layer 70 formed pattern and constitute in each pressure generating chamber 12 as public electrode.At this, constitute by certain one side electrode and the piezoelectric body layer 70 that form pattern, the part that generates the piezoelectricity biasing to two electrode application voltage is called the piezoelectrics active part.In this example, though lower electrode film 60 as the public electrode of piezoelectric element 700, with the individual electrode of upper electrode film 80 seat piezoelectric elements 700, also can be opposite when drive circuit or distribution.No matter be which kind of situation, in each pressure generating chamber, form the piezoelectrics active part.In addition, at this, by being referred to as piezoelectric actuator in conjunction with piezoelectric element 700 with by the oscillating plate that the driving of this piezoelectric element 700 produces displacement.In addition, piezoelectric body layer 70 independently is arranged in each pressure generating chamber 12, shown in Figure 66, by multilayer ferroelectric film 71 (71a～71f) constitute.

Ink jet recording head, formation possesses the part of the head unit of the ink flow path that is connected with ink cartridge, is installed in the inkjet recording device.Figure 67 is the synoptic diagram that its inkjet recording device of example is shown.Shown in Figure 67, head unit 1A and 1B with ink jet recording head, being set to its ink cartridge 2A and 2B that constitutes the providing ink means can load and unload, the shelf 3 of this head unit 1A and 1B has been installed, has been provided with to such an extent that it can move freely at its direction of principal axis of shelf axle 5 upper edges that is mounted on the device main frame 4.This head unit 1A and 1B, for example black ink constituent and Colour composition thing spue respectively.The actuating force of drive motors 6 is delivered on the shelf 3 by a plurality of gears and the sequential band 7 that does not disengage among the figure, thereby the shelf 3 of head unit 1A and 1B has been installed, move along shelf axle 5.On the other hand, on device main frame 4, be provided with pressing plate 8 along shelf axle 5, by the record seat S of the recording medium of the paper of paper feedings such as not shown paper feeding China ink rod etc., by conveyance to pressing plate 8.

In addition, be illustrated as the spue example of ink jet recording head of ink of jet head liquid, but the present invention all is an object with jet head liquid and the liquid injection apparatus that has used piezoelectric element.As jet head liquid, can be exemplified as use at the recording head of the image recording structure of printer etc., use pigment injector head in the manufacturer of the color filter of LCD etc., use electrode material injector head that the electrode at OLED display, FED (face active display) etc. forms, use in the biological organic substance injection of biological chip manufacturer first-class.

The piezoelectric element of this example because the PZTN film that above-mentioned example is related uses at piezoelectric body layer, therefore, can obtain following effect.

(1) because the total associativity in the raising piezoelectric body layer can improve piezoelectric constant.

(2) owing to can suppress the damaged of PbO in the piezoelectric body layer, therefore, thereby out of phase generation is suppressed and is added in easily in the electric boundary in the interface of the electrode of piezoelectric body layer, thereby can improve the effect as piezoelectric element.

(3) because the leakage current of piezoelectric body layer has obtained inhibition, therefore, can make the piezoelectric body layer filming.

In addition, jet head liquid of this example and liquid injection apparatus have used the piezoelectric element that comprises above-mentioned piezoelectric body layer, therefore, particularly can obtain following effect.

(4) owing to can reduce the aging of piezoelectric body layer, therefore, can suppress piezoelectric body layer displacement through the time change, thereby can improve reliability.

The above is the preferred embodiments of the present invention only, is not limited to the present invention, and for a person skilled in the art, the present invention can have various changes and variation.Within the spirit and principles in the present invention all, any modification of being done, be equal to replacement, improvement etc., all should be included within the claim scope of the present invention.

Claims

1. ferroelectric film, it is by as using ABO ₃The ferroelectric PZT of perovskite structure of expression is that ferroelectric constitutes, and it is characterized in that, comprises the Si as A position counterion on the A position ²⁺, Ge ²⁺, and Sn ²⁺In at least a, on the B position, comprise Nb as B position counterion ⁵⁺

2. ferroelectric film according to claim 1, it is characterized in that, the amount that ion is added in described A position for the ferroelectric stoichiometric ratio of described perovskite structure smaller or equal to 16 moles of %, the amount that ion is added in described B position for the ferroelectric stoichiometric ratio of described perovskite structure smaller or equal to 30 moles of %.

3. ferroelectric film according to claim 1 is characterized in that, described PZT is that ferroelectric comprises the Pb as A position ion ²⁺, and comprise Zr as B position ion ⁴⁺And Ti ⁴⁺

4. ferroelectric film according to claim 1 is characterized in that, described perovskite structure ferroelectric is by cube brilliant formation in (111) crystal orientation.

5. ferroelectric film according to claim 1 is characterized in that, described perovskite structure ferroelectric is made of the rhombohedral crystal in (001) crystal orientation.

6. ferroelectric film, it is by the conduct ABO that comprises oxygen ion defects ₃The ferroelectric PZT of perovskite structure of expression is that ferroelectric constitutes, and it is characterized in that, comprises the Si as A position counterion on the A position ²⁺, Ge ²⁺, and Sn ²⁺In at least a, on the B position, comprise Nb as B position counterion ⁵⁺, the valence mumber of described A position counterion and owing to add B position counterion the total of remaining whole B position valence mumber, smaller or equal to not enough valence mumber corresponding to described oxygen ion defects amount.

7. ferroelectric film according to claim 6 is characterized in that, the amount of described oxygen ion defects for the ferroelectric stoichiometric ratio of described perovskite structure smaller or equal to 15 moles of %.

8. according to claim 6 or 7 described ferroelectric films, it is characterized in that, the amount that ion is added in described A position for the ferroelectric stoichiometric ratio of described perovskite structure smaller or equal to 16 moles of %, the amount that ion is added in described B position for the ferroelectric stoichiometric ratio of described perovskite structure smaller or equal to 30 moles of %.

9. ferroelectric film according to claim 6 is characterized in that, described PZT is that ferroelectric comprises the Pb as A position ion ²⁺, and comprise Zr as B position ion ⁴⁺And Ti ⁴⁺

10. ferroelectric film according to claim 6 is characterized in that, described perovskite structure ferroelectric is by cube brilliant formation in (111) crystal orientation.

11. ferroelectric film according to claim 6 is characterized in that, described perovskite structure ferroelectric is made of the rhombohedral crystal in (001) crystal orientation.

12. a ferroelectric memory comprises each described ferroelectric film in the claim 1 to 11.

13. a piezoelectric device comprises each described ferroelectric film in the claim 1 to 11.